From: Curt Gregg \(cugregg\) (cugregg@cisco.com)
Date: Wed Feb 07 2007 - 11:29:08 ART
You can verify the OSPF adj is not up by via 'debug ip ospf adj' you
will see something like the following:
OSPF: Rcv DBD from 170.170.11.6 on fastethernet 0/0 seq 0xE44 opt 0x2
flag 0x7 Len 32 mtu 1500 state EXSTART
OSPF: Nbr 170.170.11.6 has larger interface MTU
Why Are OSPF Neighbors Stuck in Exstart/Exchange State?
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009
3f0d.shtml
As Brian pointed out most router interfaces will not support a higher
MTU above 1500 as the 3550/3560 switch defaults to 1504. You could
change the system MTU on the switch however that will require a reboot.
Another option would be to use 'ip ospf mtu-ignore' on the OSPF
adjancies.
Curt
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Mohammad Saeed
Sent: Monday, February 05, 2007 11:03 PM
To: Cisco certification
Subject: MTU Mismatch in OSPF
Hi Every body,
I am just wondering, how to verify the ospf adjacensy is not coming up
and reason is MTU mismatch? Like if you have set
system mtu 1504 on the switch and there are routers using that switch to
establish adjacency, they will be stuck in INIT/EXSTRAT State, what type
of debug can show that the adjacency is stuck because of MTU mismatch?
How can you change MTU to 1504 on the router interface to match if you
don't want to use ip ospf mtu-ignore command under interfaces?
Regards,
Mohammad Zahed Saeed
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